Ti Grade Research Articles

Fatigue Analysis on a Newly Designed Hip Implant with Finite Element Method

This study used Finite Element Analysis (FEA) and Reverse Engineering (RE) methods to assess the fatigue performance of an originally designed cementless hip implant. The implant prototype was initially scanned using 3D scanning technology, and a finite element model was created. The implant was analyzed under dynamic loads for six different biomaterials commonly used, namely Ti-6Al-4V (Grade5), ASTM F3046 (Ti-3Al-2.5V), ASTM F75 (CoCr), ASTM F562(MP35N), ASTM F136(Ti6Al4V ELI), ASTM F67 (Ti Grade 4), and the fatigue life was evaluated. The results showed that the ASTM F75 (CoCr) implant had the highest stress and the ASTM F67 (Ti Grade 4) implant had the lowest stress. Also, Ti6Al4V (Grade 5) implant is more resistant to fatigue than their counterparts made from ASTM F75 (CoCr), ASTM F136 (Ti6Al4V ELI) and ASTM 3046 (Ti-3Al-2.5V).

Duplex surface engineering of cold spray Ti coatings and physical vapor-deposited TiN and AlTiN thin films

The feasibility of a duplex coating based on cold spray technology and magnetron sputtering was evaluated for repair applications requiring a ‘thin-on-thick’ layered structure. Commercially pure angular-shaped Ti grade 4 particles are fed to a cold spray gun and accelerated toward a Ti alloy substrate to deposit thick coatings (∼4.5 mm). TiN and AlTiN thin films are deposited on polished cold spray coatings using a four-source closed-field unbalanced magnetron sputtering (CFUBMS) system. Microstructure was characterized using focused ion beam (FIB) lift-out, scanning electron microscopy (SEM), and electron channeling contrast imaging (ECCI). The nanoindentation technique was used to evaluate the mechanical properties of coatings. The H/E ratios and H3/E2 ratios for TiN films were found to be 0.098 and 0.26 GPa, respectively, while those for AlTiN films were measured at 0.066 and 0.052 GPa, respectively, suggesting higher capacity of TiN films to withstand both elastic and plastic deformation. Using scratch testing, the adhesion of TiN and AlTiN thin films to cold spray Ti was investigated, with TiN-Ti duplex coatings exhibiting better performance compared to AlTiN-Ti coatings. Tribological testing was performed on duplex coatings using a reciprocating tribometer equipped with an alumina ball counterface. The wear rate for AlTiN-Ti coatings after 2000 sliding cycles was found to be (1.0 × 10−3 ± 0.1 × 10−3 mm3/Nm), three orders of magnitudes higher than that for TiN-Ti (8 × 10−6 ± 2 × 10−6 mm3/Nm. SEM was used to reveal worn surface morphologies and cross-sectional analysis of the wear track. Subsurface microstructural changes due to wear were examined using focused ion beam cross-sectioning, revealing bending cracks and tribofilm formation.

Multi-objective parametric optimization process of hybrid reinforced titanium metal matrix composite through Taguchi-Grey relation analysis (TGRA)

Hybrid titanium metal matrix composites (HTMMCs) are advanced composite materials that can be tailored to a variety of applications. Because of their decreased fuel consumption and cost, they are popular in the transportation industry. Using multi-objective optimization and Taguchi-based Grey relational analysis (TGRA), this study investigates the impact of hybrid reinforced HTMMCs synthesized using powder metallurgy on their physic mechanical properties. The research investigates reinforcements such as B4C, SiC, ZrO2, and MoS2 at various compaction pressures, milling durations, and sintering temperatures. The best powder metallurgy control parameters for HTMMC synthesis, with a milling time of 5 h, a compaction pressure of 40 MPa, a sintering temperature of 1200 °C, and a sintering time of 1 h, and a compaction time of 40 min. According to validation results, HTMMC material with optimized process parameters had experimental densities, porosities, hardness, compressive strength, and wear rates of 4.29 gm/cm3, 0.1178%, 71.53RHN, 2782.36 MPa, and 0.1519 mm3 correspondingly. The material hardness was increased by 1.99% and compressive strength by 2.87%. The use of Taguchi and GRA techniques strongly verified that the impact of milling duration and sintering temperature was the greatest of all five factors. The novel synthesized hybrid reinforcing HTMMCs outperformed pure Ti grade 5 and single and double fortified HTMMCs in terms of physic mechanical characteristics. As a result, the newly developed tetra hybrid reinforced HTMMC material is expected to be used in heavy-duty vehicles, aerospace, automobiles, maritime, and other industries.

Preparation of Ti3AlC2/Al2O3 composites based on the titanium concentrate: Gas-based reduction, acid leaching and sintering

Ti3AlC2/Al2O3 composites exhibit outstanding physical and chemical properties, but their widespread use is hindered by the expensive raw materials. This study introduces a novel production process for Ti3AlC2/Al2O3 composites. Initially, high grade Ti(C, O) powders with purity above 90 % are obtained through the reduction and carbonization of titanium concentrate in a CH4–H2 system. Subsequently, pure Ti3AlC2/Al2O3 composites are fabricated via sintering using the Ti(C, O)/Ti/Al system. Experimental findings reveal that prolonged reduction time and high temperatures in the CH4–H2 system lead to increased carbon deposition in the titanium concentrate reduction product, adversely impacting the purity of the sintered Ti3AlC2/Al2O3 composites. The optimal conditions for reducing titanium concentrate to Ti(C, O) in the CH4–H2 system involve a 1.5-h reduction period at 1200 °C. Excess Ti and Al powders are crucial in the preparation of Ti3AlC2/Al2O3 composites from the Ti(C, O)/Al/Ti material system. Surplus Ti powders reduce the TiC content in the final product, while excess Al powders act as deoxidizers, removing oxygen from Ti(C, O) and generating Al2O3 in situ. The optimal molar ratio for Ti(C, O), Al and Ti powders is determined to be 2:1.6:1.2. This research introduces a cost-effective approach for producing pure Ti3AlC2/Al2O3 composites.

Mechanical Properties of Ti Grade 2 Manufactured Using Laser Beam Powder Bed Fusion (PBF-LB) with Checkerboard Laser Scanning and In Situ Oxygen Strengthening

Additive manufacturing (AM) technologies have advanced from rapid prototyping to becoming viable manufacturing solutions, offering users both design flexibility and mechanical properties that meet ISO/ASTM standards. Powder bed fusion using a laser beam (PBF-LB), a popular additive manufacturing process (aka 3D printing), is used for the cost-effective production of high-quality products for the medical, aviation, and automotive industries. Despite the growing variety of metallic powder materials available for the PBF-LB process, there is still a need for new materials and procedures to optimize the processing parameters before implementing them into the production stage. In this study, we explored the use of a checkerboard scanning strategy to create samples of various sizes (ranging from 130 mm3 to 8000 mm3 using parameters developed for a small 125 mm3 piece). During the PBF-LB process, all samples were fabricated using Ti grade 2 and were in situ alloyed with a precisely controlled amount of oxygen (0.1–0.4% vol.) to enhance their mechanical properties using a solid solution strengthening mechanism. The samples were fabricated in three sets: I. Different sizes and orientations, II. Different scanning strategies, and III. Rods for high-cycle fatigue (HCF). For the tensile tests, micro samples were cut using WEDM, while for the HCF tests, samples were machined to eliminate the influence of surface roughness on their mechanical performance. The amount of oxygen in the fabricated samples was at least 50% higher than in raw Ti grade 2 powder. The O2-enriched Ti produced in the PBF-LB process exhibited a tensile strength ranging from 399 ± 25 MPa to 752 ± 14 MPa, with outcomes varying based on the size of the object and the laser scanning strategy employed. The fatigue strength of PBF-LB fabricated Ti was 386 MPa, whereas the reference Ti grade 2 rod samples exhibited a fatigue strength of 312 MPa. Our study revealed that PBF-LB parameters optimized for small samples could be adapted to fabricate larger samples using checkerboard (“island”) scanning strategies. However, some additional process parameter changes are needed to reduce porosity.

Friction and heat partition coefficients in incremental sheet forming process

To understand the thermo-mechanical behaviour in incremental sheet forming (ISF), it is important to precisely determine the interfacial and thermal-relevant parameters including coefficient of friction (COF) and heat partition coefficient (HPC), and to characterise the effect of thermo-mechanically induced heat generation under ISF processing conditions. In the present study, a new tool path-defined straight groove test combined with mechanical and thermal detection is proposed to determine the COF and HPC of Aluminium alloy (AA1050) and commercially pure titanium Grade 1 (CP Ti Grade 1) sheets. The experimental and numerical results show that the determined COF and HPC values are sufficiently accurate. The interaction between friction force and thermal response is observed by this testing method. A novel theoretical thermal model is developed to correlate the relationship between friction-induced heat generation and the thermal effect. The results indicate that the new theoretical model can capture the temperature distribution and variation under different processing conditions, and the results show a good agreement with the finite element (FE) simulation. The presented testing method and theoretical model provide an insight into the determination of the thermal-relevant parameters (COF and HPC), and the quantification of the effect of friction-induced heat generation on the thermal response of the materials.

An integrated investigation of the effect of sub-transus treatment on the microstructure and corrosion behaviour of the LPBF Ti–6Al–4V alloy

Biomedical grade Ti–6Al–4V alloy, is the best candidate material for bioimplants due to its outstanding corrosion resistance. Additive manufacturing processes such as laser-based powder bed fusion (LPBF) are trending technologies that challenge conventional manufacturing methods in producing customized implants. However, the Ti–6Al–4V alloy fabricated by LPBF consists of a non-equilibrium phase (α′-martensite), that tends to degrade the corrosion resistance, and therefore a post-treatment is required to stabilize the phases. In this work, the annealing is done in the α+β range of the Ti–6Al–4V alloy. The corrosion performances of the as-built (AB) and annealed samples in 0.9 wt% NaCl solution are investigated through electrochemical measurements. The relationship between the microstructure and its corresponding corrosion behaviour is elucidated. The rate of corrosion increased by around 12 % following low temperature annealing, but decreased by more than 50 % following high temperature annealing above 850 ᵒC. Overall, the AB structure shows an inferior corrosion behaviour compared to the annealed ones. The electrochemical results show that post-annealing has a positive effect on corrosion performance that can be ascribed to various factors such as phase fraction, chemical composition, morphological features of microstructural and presence of defects. The findings show that a microstructure with increased β-phase fraction, a fine lamellar structure with low defect density, and a comparatively coarser grain size is beneficial in improving corrosion resistance. This can be achieved by annealing the Ti–6Al–4V alloy at 850 ᵒC or higher.

Optimization of porosity behavior of hybrid reinforced titanium metal matrix composite through RSM, ANN, and GA for multi-objective parameters

Titanium matrix composites (TMCs) have high specific strength and stiffness, and high-temperature TMCs can reduce weight by up to 50% when compared with monolithic super alloys while preserving equal stiffness and strength in jet engine systems for propulsion. The purpose of this work examines the use of mathematical models and learning approaches to optimize response such as porosity and control variables in synthesized hybrid titanium metal matrix composites (HTMMCs) reinforced by B4C-SiC-MoS2-ZrO2. To further understand the impacts of process factors on porosity reduction, the study employs methodologies such as the response surface methodology (RSM), integrated artificial neural networks (ANN), and genetic algorithm (GA). The findings indicate that these strategies have the potential to contribute to the industry. The optimal combination of 7.5wt.% SiC, 7.5wt.% B4C, 7.5wt.% ZrO2, 4wt.% MoS2, and 73.5wt.% Ti compositions was determined utilizing process factors such as milling period (6h), compaction pressure (50MPa), compact duration (50min), sintering temperature (1200°C), and sintering time (2h) as compared to pure Ti grade 5. The mechanical properties of the optimum combination of reinforcement weight percentage and process parameters resulted in a minimum porosity of 0.118%, density of 4.36gcm3, and micro-hardness of 63.4HRC boosted by 1.76%, and compressive strength of 2500MPa increased by 2.6%. In addition, these HTMMCs had a minimal wear rate of 0.176mm3/Nm and a corrosion resistance rate of 2.15×10-4mmpy. The investigation result analysis discovered that the RSM and combined ANN-GA models considerably enhanced the forecasting of multidimensional interaction difficulties in composite material production that were highly statistically connected, with R2 values of 0.9552 and 0.97984. The ANN-GA model provided a 95% confidence range for porosity predictions, which increased the production use of titanium-based particle composites. Furthermore, HMMCs can be utilized in the automotive and aviation industries with enhanced corrosion and wear resistance.

How to suppress the Kirkendall porosity within the Ti/Ni explosive welds?

Pure Ti (Grade 1) and Ni (type Ni201) were used to produce the Ti/Ni welds employing the explosive welding process. Thermal expansion of the welded plates was determined using dilatometric measurements from room temperature up to 600 °C. The results showed that the thermal expansion coefficient of Ti/Ni welded plates is closer to that of pure nickel than would be suggested by the Timoshenko’s model for bimetallic strip. The microstructure of the Ti/Ni interface after exposure to high temperatures revealed the presence of extensive interface porosity (Kirkendall porosity). This may cause a catastrophic disintegration of the weld during working or essential forming. The welded plates were annealed at the temperature of 650 °C under different applied compressive loads, and the applied load was shown to alter the microstructure of the NixTiy phases present at the Ti/Ni interface. Based on the obtained interface microstructural data, the strategy to suppress the Kirkendall porosity at the interface was proposed.

Effect of grinding parameters and coolants on grindability of Ti grade 9 alloy

For many years, surface roughness has drawn considerable attention, and it is a crucial design element in a variety of circumstances, including components sensitive to fatigue stresses, precision fittings, fastener holes, and aesthetic demands. Grinding the is best conventional machining process to achieve a better surface finish on a given component. Titanium 3Al-2.5 V or Ti grade 9 alloy is primarily utilized in the biomedical, aerospace, and automotive sectors. But because of its low heat conductivity, high chemical reactivity and rapid work hardening, this alloy is known as a difficult-to-cut material. In grinding, the abrasives have low thermal conductivity and small chip sizes, which in turn more heat to being focused in the cutting zone. This heat harms the surface of the workpiece. Therefore, it's crucial to regulate the quantity of heat that the workpiece receives.In this context, this work examines the surface quality of the Titanium 3Al-2.5 V alloy following surface grinding with an Al2O3 wheel under various grinding settings, including surface roughness (Ra), microhardness and material removal rate (MRR) from the workpiece. Techniques for delivering coolant conventionally (flood coolant), dry and using MQL were used and grinding performance were evaluated. The findings demonstrated that the Ra varied from 0.32 to 0.594 µm and hardness on the machine surface varied from 61.7 to 72 HRC. The MRR varied from 0.09 to 0.42 g/minute for the changes in depth of cut, table feed and coolants. Overall, the MQL has produced a good surface finish, high MRR and moderate hardness on the workpiece.

Morphology and Structure of TiO2 Nanotube/Carbon Nanostructure Coatings on Titanium Surfaces for Potential Biomedical Application.

Titanium is the most used material for implant production. To increase its biocompatibility, continuous research on new coatings has been performed by the scientific community. The aim of the present paper is to prepare new coatings on the surfaces of the pure Ti Grade 2 and the Ti6Al4V alloy. Three types of coatings were achieved by applying anodization and chemical vapor deposition (CVD) methods: TiO2 nanotubes (TNTs) were formed by anodization, carbon nanotubes (CNTs) were obtained through a metal-catalyst-free CVD process, and a bilayer coating (TiO2 nanotubes/carbon nanostructures) was prepared via successive anodization and CVD processes. The morphology and structure of the newly developed coatings were characterized using SEM, EDX, AFM, XRD, and Raman spectroscopy. It was found that after anodization, the morphology of the TiO2 layer on pure Ti consisted of a "sponge-like" structure, nanotubes, and nano-rods, while the TNTs layer on the Ti alloy comprised mainly nanotubes. The bilayer coatings on both materials demonstrated different morphologies: the pure Ti metal was covered by a layer of nanotubular and nano-rod TiO2 structures, followed by a dense carbon layer decorated with carbon nanoflakes, and on the Ti alloy, first, a TNTs layer was formed, and then carbon nano-rods were deposited using the CVD method.

Drilling of Ti Grade‐2 Alloy Using WC Tool in Micro‐EDM and Its Multiparameter Optimization

In this study, microelectrical discharge machining (μEDM) is used for drilling microholes on a thin sheet of Ti Grade 2 alloy of thickness 50 μm using a tungsten carbide (WC) microtool of diameter 470 μm. The main focus of the study is to understand the electrical and nonelectrical μEDM parameters on the accuracy, precision, and machining efficiency of drilled holes. The controllable process factors such as capacitance, voltage, tool rotation, and feed rate are considered when conducting the experiments based on a Taguchi L16 orthogonal array. The main effect and interaction contour plots have been prepared to investigate the influence of the process parameters on the response measures like material removal rate, overcut, circularity, and taper angle of the drilled holes. Analysis of variance (ANOVA) has been carried out to study the percentage contribution and significance of each process parameter on the performance measures. The micrographic images reveal the quality of the profiles and edges of the drilled holes. Further, the Overall Evaluation Criterion (OEC) is applied for multiparameter optimization.

Polymorphous nanostructured metallic glass coatings for corrosion protection of medical grade Ti substrate

Metallic glasses have received attention in the world of materials science and engineering due to their high mechanical and tribological properties. Thin film nanostructured metallic glasses have shown great prospects as surface coatings with increasing applications in biomedical areas for implants and surgical devices. In this work, we deposited titanium- and zirconium-based polymorphous thin film metallic glasses (Ti–Fe–Cu, Zr–Fe–Al, Zr–W–Cu) on medical-grade polished titanium substrate by co-sputtering using a PVD system. The corrosion behaviour of the films was investigated by exposing the samples to sterile simulated body fluid and examined using electrochemistry, microscopy, and spectroscopic analyses. The polymorphic properties of the films after exposure to simulated body fluid were observed by SEM and TEM. SEM analysis shows that the surface morphology of the exposed samples was found to vary significantly compared to their corresponding as-deposited samples. Electrochemical properties (Ecorr, Icorr, and OCV, impedance |Z|) demonstrated that the thin film metallic glasses were found to enhance the corrosion resistance of the substrate. Further investigations of the exposed films by XPS and Raman analyses have revealed that the induced oxide passive layer significantly enhanced the corrosion efficacy of the films on titanium substrate. Among the three samples, Zr–W–Cu coating has shown the highest corrosion protection almost 450 times better than the bare titanium substrate.

Photo-Chemical Sucralose Degradation in an Aqueous Medium Using a Photo-Fenton System Equipped with Stainless Steel Mesh Cathodes Modified By Nanostructured TiO2- and C|TiO2-Based Films for Continuous Electro-Generation of H2O2

Artificial non-caloric sweeteners are non-bioassimilable substances that pass through the human body without biochemical changes. Sucralose, for instance, is 600 times sweeter than natural sucrose, so it is widely used in beverages and processed food products without regulation in many countries. Its environmental persistence of 337 days in sludge allows inferring that these substances can adversely affect the environment in the short or long term, thus classifying sucralose as an emergent pollutant. In this work, stainless steel (SS) mesh working electrodes were modified by TiO2- or C|TiO2-based nanoparticulate films (where C is carbon Vulcan). Both types of electrodes were employed as cathodes for the electro-generation of hydrogen peroxide (H2O2), which was the chemical precursor for photochemical producing •OH radicals able for sucralose degradation in a photo-Fenton system equipped with a 254 nm light source. Preparation of TiO2- and C|TiO2-based cathodes was performed by electrophoretic deposition method (EPD, 2 V/cm for 40 s) on AISI 304 SS mesh, followed by sintering at 450°C for 1h in the air. The EPD process was performed using aqueous colloidal suspensions containing wt./wt. ratios of C/TiO2 = 1/100 and 1/10, or TiO2 without C for comparison purposes. H2O2 electro-generation was carried out via Reaction 1 utilizing a two-electrode cell (3V-cell polarization) containing sucralose dissolved in a pH 2 aqueous sulfates buffer solution perpetually bubbled by air (volumetric flow rate of 17 mL/s) containing gaseous O2. In all the cases, a Ti grade 2.0 rod anode was immersed in the electrolyte medium with one of the following cathodes: SS* (polished, degreased, and heated at 450°C for 1h in the air as control electrode), SS||TiO2 and SS||C|TiO2 (wt./wt. ratios of C/TiO2 = 1/100 or 1/10). Furthermore, the cell was illuminated by a 254 nm lamp in order to continuous promotion of the photo-chemical Reaction 2.O2 + 2H+ + 2e- → H2O2 ...............(1)H2O2 254mn→ 2°OH...................... (2)Sucralose degradation efficiencies were registered based on the cathodes employed for continuous H2O2 electro-generation. Furthermore, the relative use time was also registered for each cathode. A comparison of these results reveals that when employed SS*, SS||TiO2, and SS||C|TiO2 (wt./wt. ratio of C/TiO2=1/100) cathodes the sucralose degradation achieved efficiencies over 90% (i.e. 99.1, 96.8, and 91.3%, respectively). In contrast, SS||C|TiO2 (wt./wt. ratio of C/TiO2=1/10) cathodes showed a sucralose degradation efficiency of only 88.6%. Furthermore, the SS||TiO2 and SS||C|TiO2 cathodes showed durability 3 times higher than for the SS* cathodes, and 1.8 times higher than for SS||C|TiO2 (wt./wt. ratio of C/TiO2=1/10). These observations indicated that both, SS||TiO2 and SS||C|TiO2 cathodes are strong candidates for assembling more efficient photo-Fenton systems for the degradation of sucralose and other artificial sweeteners.

The effect of three dental cement types on the corrosion of dental implant surfaces

Statement of problemOne of the main challenges facing dental implant success is peri-implantitis. Recent evidence indicates that titanium (Ti) corrosion products and undetected-residual cement are potential risk factors for peri-implantitis. The literature on the impact of various types of dental cement on Ti corrosion is very limited. PurposeThis study aimed to determine the influence of dental cement on Ti corrosion as a function of cement amount and type. Materials and methodsThirty commercially pure Ti grade 4 discs (19 × 7mm) were polished to mirror-shine (Ra ≈ 40 nm). Samples were divided into 10 groups (n = 3) as a cement type and amount function. The groups were no-cement as control, TempBond NE (TB3mm, TB5mm, and TB8mm), FujiCEM-II (FC3mm, FC5mm, and FC8mm), and Panavia-F-2.0 (PC3mm, PC5mm, and PC8mm). Tafel’s method estimated corrosion rate (icorr) and corresponding potential (Ecorr) from potentiodynamic curves. Electrochemical Impedance Spectroscopy (EIS) data was utilized to obtain Nyquist and Bode plots. An equivalent electrical circuit estimated polarization resistance (Rp) and double-layer capacitance (Cdl). Inductively coupled plasma mass spectrometry (ICP-MS) analysis was conducted to analyze the electrolyte solution after corrosion. pH measurements of the electrolyte were recorded before and after corrosion tests. Finally, the corroded surface was characterized by a 3D white-light microscope and scanning electron microscope. Statistical analysis was conducted using either one-way ANOVA followed by Tukey’s Post Hoc test or Kruskal-Wallis followed by Dunn’s test based on data distribution. ResultsBased on cement amount, FC and PC significantly increased icorr in higher amounts (FC8mm-icorr = 8.22 × 10−8A/cm2, PC8mm-icorr = 5.61 × 10−8A/cm2) compared to control (3.35 × 10−8A/cm2). In contrast, TB3mm decreased icorr significantly compared to the control. As a function of cement type, FC increased icorr the most. EIS data agrees with these observations. Finally, corroded surfaces had higher surface roughness (Ra) compared to non-corroded surfaces. ConclusionThe study indicated that cement types FC and PC led to increased Ti-corrosion as a function of a higher amount. Hence, the implant stability could be impacted by the selection, excessive cement, and a potentially increased risk of peri-implantitis.

Structural, thermal and acoustic aspects of crack propagation in titanium alloys

The aim of this work was to investigate the correlation between structural, acoustic emission and thermal characteristics of the fatigue crack growth in titanium alloys. Cluster analysis of the acoustic emission signals revealed two different types of signals recorded during the development of a fatigue crack. It has been shown experimentally that the evolution of the stored energy tends to an asymptotic value at the final stage of fatigue crack growth and it correlates with the intensification of the twinning process in titanium alloy Ti Grade 2. A correlation was assumed between the stages of change in the heat flux, the cumulative energy of the first cluster of AE signals and the crack length.

Comparative Wire Electrical Discharge Machining Performance Studies on SS304 and Ti Grade 9 Alloys

Comparative Wire Electrical Discharge Machining Performance Studies on SS304 and Ti Grade 9 Alloys

Comparative evaluation of osseointegration of new percutaneous implants made of Ti Grade 4 ultrafine‑grained alloy

Introduction It has been shown that titanium implants with a structured surface provide an increased rate of osseointegration what makes their application quite promising.The purpose of this work was to conduct a comparative evaluation of the efficiency of osseointegration of new percutaneous implants for prosthetics made of ultrafine-grained Ti Grade 4 alloy.Materials and methods The study was carried out on 12 male rabbits of the Soviet Chinchilla breed. Six rabbits of the control group had implants made of Ti6Al4V powder using selective laser sintering technology that were osseointegrated into the tibia, 6 rabbits of the experimental group had implants made of Ti Grade 4 by equal channel angular pressing. The formation of the "bone-implant" block was examined 26 weeks after the implantation.Results Histologically, after 26 weeks of the experiment, porous changes, enlargement of the Haversian canals, and pronounced osteoclastic resorption were not detected in the animals of the experimental group throughout the stump in the compact plate. Around the implant, a bony case repeating the bone shape was formed, represented by lamellar bone tissue. Using X-ray electron probe microanalysis, it was found that in the substrate formed on the surface of the implant in rabbits of the experimental group, there was significantly more calcium in all areas over the implant relative to the animals of the control group. In the control group, relative to the experimental group, an increased level of C-reactive protein in blood serum was retained longer. Complications and significant clinical and laboratory abnormalities were not found in both groups during the entire experiment.Discussion Our data are consistent with the results of other experimental studies, which unambiguously noted that titanium implants with a structured surface show increased osseointegration characteristics in comparative studies relative to implants without modification of the structure of the material of the threaded surface. The absence of complications and undesirable reactions of the animal organism also indicates the acceptable safety of the tested products.Conclusion Osseointegration of a percutaneous implant that has a mixed nanocrystalline and ultrafine-grained structure was more effective than the reference implant. This makes the use of such implant promising for solving clinical problems in prosthetics.

Improvement of selective laser melting regimes for the fabrication of Ti–6Al–4V porous structures for medical applications

This article describes approaches to the optimization of regimes of selective laser melting (SLM) used in the fabrication of porous materials from medical grade Ti–6Al–4V alloy with thin structural elements and a low level of defect porosity. Improved fusion of thin elements based on SLM regimes is achieved due to a significant decrease in the distance between laser passes (from 0.11 to 0.04–0.05 mm). Moreover, the balance between the laser energy density and building rate is compensated by changing the laser speed and laser power. The results of the study of defect porosity and hardness of samples fabricated according to experimental SLM regimes allowed three promising sets of parameters to be defined. One was selected for studying mechanical properties in comparison with the reference SLM regime. In the aims of this study, the samples were developed and fabricated using the structures of rhombic dodecahedron and Voronoi types with a porosity of 70–75 %. The decrease in defect porosity was established at ≈1.8 % to 0.6 %, depending on the SLM regime. This promotes a significant increase in strength properties of the material, including an increase in the yield strength of rhombic dodecahedron from 76 to 132 MPa and the Voronoi structure from 66 to 86 MPa. The low Young module (1–2 GPa) remains, corresponding to the rigidity level of spongy bone tissue.

The Effect of Microstructural Defects on High-Cycle Fatigue of Ti Grade 2 Manufactured by PBF-LB and Hydrostatic Extrusion

The aim of this study was to show the effect of manufacturing defects in a commercially pure Ti Grade 2 produced by a laser beam powder bed fusion (PBF-LB) process on its high-cycle fatigue life. For this purpose, the high-cycle fatigue performance of PBF-LB Ti Grade 2 was compared to its ultrafine-grained (UFG) counterpart processed by hydrostatic extrusion exhibiting a similar mechanical properties under static tensile. The yield strength of the PBF-LB and UFG Ti Grade 2 was 740 and 783 MPa, respectively. The PBF-LB Ti Grade 2 consisted of a typical columnar of prior β grains with an acicular martensite α’ microstructure, while UFG Ti Grade 2 was mainly composed of fine, equiaxed α phase grains/subgrains with a size of 50–150 nm. A residual porosity of 0.21% was observed in the PBF-LB Ti Grade 2 by X-ray computed tomography, and, despite similar yield strength, a significantly higher endurance fatigue limit was noticed for UFG Ti Grade 2 (420 MPa) compared to PBF-LB Ti Grade 2 (330 MPa). Fatigue striation analysis showed that the fatigue crack propagation rate was not affected by manufacturing technology. In turn, the high-cycle fatigue life was drastically reduced as the size of manufacturing defects (such as pores or lack of fusion zones) increased.